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Question #47461
The Question
A patient diagnosed with Myasthenia Gravis exhibits progressive skeletal muscle fatigue and a clinically diminished patellar reflex. Electrophysiological studies reveal an abnormally high 'reflex arc latency'. Which of the following best explains the precise physiological basis for this observation?
Options
- A.
Autoantibodies degrade the myelin sheath of the efferent somatic motor neurons, reducing saltatory conduction velocity.
- B.
Autoantibodies block postsynaptic acetylcholine receptors at the motor end plate, prolonging synaptic delay as the threshold potential is inadequately reached.
- C.
Autoantibodies inhibit acetylcholinesterase in the synaptic cleft, causing prolonged depolarization and subsequent receptor desensitization.
- D.
Autoantibodies destroy voltage-gated calcium channels on the presynaptic membrane, halting the exocytosis of neurotransmitter vesicles.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Reflex Arc Latency|Autoimmunity Principles|Acetylcholine
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Differentiating the exact anatomical and physiological targets of various neuromuscular disorders.
Common Misconception: Students often know Myasthenia Gravis causes 'muscle weakness' (NCERT fact) but fail to apply this to reflex arc electrophysiology.
By introducing 'reflex arc latency', the question tests if the student understands that postsynaptic receptor blockage directly increases synaptic delay by preventing the motor end plate from rapidly reaching the threshold potential.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Reflex Arc Latency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |